Evolution of magnetic and dielectric properties in Sr-substituted high-temperature multiferroic YBaCuFeO ₅

Abstract

We report the evolution of structural, magnetic and dielectric properties due to partial substitution of Ba by Sr in the high temperature multiferroic YBaCuFeO 5 . This compound exhibits ferroelectric and antiferromagnetic transitions around 200 K and these two phenomena are presumed to be coupled with each other. Our studies on magnetic and dielectric properties of the YBa 1-x Sr x CuFeO 5 (x = 0.0, 0.25 and 0.5) show that substitution of Sr shifts magnetic transition towards higher temperature whereas dielectric transition to lower temperature. These results points to the fact that magnetic and dielectric transitions get decoupled as a result of chemical pressure in form of Sr substitution. The nature of magnetodielectric coupling changes across the series with the presence of higher order coupling terms. Additionally in these compounds glassy dynamics of electric dipoles is observed at low temperatures.

Effect of doping of Co, Ni and Ga on magnetic and dielectric properties of layered perovskite multiferroic YBaCuFeO5

“…All the peaks fit well with the theoretical curve and no impurity peak is observed which indicates that all the compounds are formed in crystallographic single phase. The structure of these compounds is similar to that reported in literature [9,15,16]. The partial replacement of Fe with Co, Ni and Ga results in small changes in the structural parameters of the unit cell in comparison to YBaCuFeO 5 due to variation in the ionic radii.…”

“…Polycrystalline samples of YBaCuFe 0.85 Co 0.15 O 5 (Co_0.15), YBaCuFe 0.85 Ni 0.15 O 5 (Ni_0. 15) and YBaCuFe 0.85 Ga 0.15 O 5 (Ga_0.15) are synthesized by solid-state reaction method similar to that reported in literature [9,14]. Power x-ray diffraction is performed using Regaku smart lab diffractometer using monochromatized CuKα 1 radiation at room temperature.…”

“…However, the interaction between the electric dipoles is not strong enough for collective freezing of the electric dipoles. The partial replacement of Ba with Sr leads the dipolar glass behavior at low temperature [9]. However, this low temperature behavior is absent in Co, Ni and Ga doped compounds.…”

“…YBaCuFeO 5 shows the magneto-dielectric coupling at different temperatures [8,9]. To see the effect of MDE coupling due to these substitutions, the magnetic field response of the dielectric constant is measured at 200 K at a fixed frequency of 50 kHz.…”

“…Inset of (b) shows the pattern in an expanded form for one peak for all the compounds, to bring out that the peaks shift with substitution. The data of the YBaCuFeO 5 is taken from Ref[9] for comparison. Inset of figure 1 (b) show the shifting of x-ray diffraction peak with substitution.…”